Book Image

Data Cleaning and Exploration with Machine Learning

By : Michael Walker
Book Image

Data Cleaning and Exploration with Machine Learning

By: Michael Walker

Overview of this book

Many individuals who know how to run machine learning algorithms do not have a good sense of the statistical assumptions they make and how to match the properties of the data to the algorithm for the best results. As you start with this book, models are carefully chosen to help you grasp the underlying data, including in-feature importance and correlation, and the distribution of features and targets. The first two parts of the book introduce you to techniques for preparing data for ML algorithms, without being bashful about using some ML techniques for data cleaning, including anomaly detection and feature selection. The book then helps you apply that knowledge to a wide variety of ML tasks. You’ll gain an understanding of popular supervised and unsupervised algorithms, how to prepare data for them, and how to evaluate them. Next, you’ll build models and understand the relationships in your data, as well as perform cleaning and exploration tasks with that data. You’ll make quick progress in studying the distribution of variables, identifying anomalies, and examining bivariate relationships, as you focus more on the accuracy of predictions in this book. By the end of this book, you’ll be able to deal with complex data problems using unsupervised ML algorithms like principal component analysis and k-means clustering.
Table of Contents (23 chapters)
1
Section 1 – Data Cleaning and Machine Learning Algorithms
5
Section 2 – Preprocessing, Feature Selection, and Sampling
9
Section 3 – Modeling Continuous Targets with Supervised Learning
13
Section 4 – Modeling Dichotomous and Multiclass Targets with Supervised Learning
19
Section 5 – Clustering and Dimensionality Reduction with Unsupervised Learning

Section 2 – Preprocessing, Feature Selection, and Sampling

Anyone who has done a log transformation of a target, or scaled a feature, appreciates just how critical to our analysis preprocessing can be. Raise your hand if you were ever confident that your model approximated truth, but then tried a fairly obvious transformation and appreciated just how far from truth your original model was. Encoding, transforming, and scaling data is not a gimmick, though sometimes people have that impression. We apply that preprocessing because 1) it gets us closer to capturing a real-world process and 2) because many machine learning algorithms just work better with scaled data.

Feature selection is equally important. A good adage is never build a model with N features, when N - 1 features will do just as nicely. It is worth remembering that this is more complicated than having too many features. There are times when having 3 features is too many and others when having 103 features is perfectly...